1. Field of the Invention
The present invention relates to a semiconductor device, a wafer structure and a fabrication method thereof, and more particularly, to a semiconductor device integrated with a micro-electro-mechanical system (MEMS) device and a logic device and a wafer structure and a fabrication method thereof.
2. Description of the Prior Art
Micro-electro-mechanical system (MEMS) technology is to fabricate micro mechanical devices by using conventional semiconductor technologies such as electroplating, etching such that a mechanical component in a micro-meter scale may be formed. The MEMS device may be, for example, the voltage controlling component in an ink printer, the gyroscope in a car to detect the tilt of the car, or the vibration membrane in a microphone to sense a sound. Therefore, the fabrication method of MEMS combines the fabrication process of the MEMS device with the fabrication process of the complementary metal-oxide-semiconductor (CMOS) device to integrate the MEMS device and the CMOS device into a single chip. In addition, the integrated chips can be fabricated on one wafer simultaneously, so that the MEMS technology which combines the fabrication process of the mechanical and the electronic devices has the advantages of low cost, high performance and high density.
In a integrated structure of the MEMS device and the MOS device, in order to fabricate the MEMS device that has a mechanical characteristic, such as vibration, a dielectric layer surrounding or covering the MEMS device should be removed, but in order to maintain operation of the MOS device used to transfer signals, the dielectric layer surrounding the MOS device and metal-interconnect structure should be retained. Since the process of removing the dielectric layer surrounding the MEMS device includes an isotropic etching process, various contaminations or blemishes resulting in damage of devices are often generated in the etching process to affect the operation of the MEMS device.
For this reason, to solve the problem of the MEMS device being affected by the isotropic etching process is an objective in industry.